用MASK方法传送不规则位图

HDC hDC1 = ::CreateCompatibleDC(hdcDest);

ASSERT ( hDC1 );

HBITMAP hBitmap2 = ::CreateCompatibleBitmap(hdcDest, nWidth, nHeight);

HBITMAP hOldBitmap2 = (HBITMAP)::SelectObject(hDC1, hBitmap2);

ASSERT ( hOldBitmap2 );

// 2.2 draw dest bitmap and mask

DWORD dwRop3 = BACK_ROP3(dwRop);

::BitBlt(hDC1, 0, 0, nWidth, nHeight, hdcSrc, nXSrc, nYSrc, SRCCOPY);

::BitBlt(hDC1, 0, 0, nWidth, nHeight, hdcDest, nXDest, nYDest, dwRop3);

::BitBlt(hDC1, 0, 0, nWidth, nHeight, hDCMask, xMask, yMask, DSTERASE);

// 3. make masked Foreground bitmap

// 3.1 make bitmap

HDC hDC2 = ::CreateCompatibleDC(hdcDest);

ASSERT ( hDC2 );

HBITMAP hBitmap3 = ::CreateCompatibleBitmap(hdcDest, nWidth, nHeight);

HBITMAP hOldBitmap3 = (HBITMAP)::SelectObject(hDC2, hBitmap3);

ASSERT ( hOldBitmap3 );